Thermostatic device for varying magnetic field.



' J. K. STEWART. I I THERMOSTATIG DEVICE FOR VARYIN G MAGNI ITEQfi ELD APPLICATION FILED JAN.18, 1913.

1,082,566. Patenteli' bec. 30,191

had ms Nnms'mm m LKI'HLJVASNING'ON U TED T TES. rA ENT cl rion;

"r6313. srnwanr, or CHICAGO, Inmnmsassrenon 'ro srnwnntnwnnnnn srn in- 'omn'rnn C,ORB ORA'1IO1\T, or CHICAGO, ILLINOIS, A CORPORATION or VIRGINIA. v

' -'1HERMOSTATIC nnvicn FOR VARYING MAGNETIC FIELD.

.5011 whom it mag concern:

Be it known that I, J QHN K. STEWART, a ;cit izen of the United States, residing at Chica-go, in. the county of Cook and State of .lllinois, have invented -new and useful Imio veineiits in Thermostatic Devices for ar'ying. Magnetic Field, of which the following is a specification, reference being had ,t'Q. -the accompanying drawings, forming a iiart thereof.

compensate for variations-of this magneticdrag due to variations in temperature by lierinostatically causing a corresponding iggariation of-th'e magnetic field affecting the Erie'n-iinagnetic element. V p

consists of the features and elements {described and'shown in the drawings as in- 25 jiicated'in the claims. I

the drawings :'Figure 1 is a face View zp'f a magnetic; speedometer embodying this' invention, Fig. 2 is an interior plan view iioffthe principal; elements, being taken as a' 3 section at line on Fig. 1. Fig. 3 is aftertical section taken asf indicated at line .'3'3onFig.2.' p

"The'structure shown in the drawings com prises a magnet, 1, which, as illustrated, is ?5 .ann.ular with a reduced portion at one side. Themagnetis niounted on a carrier,-2, fixed upon the shaft, 3, which is adapted to be connected with any shaft or wheehwhose speed of rotation is to be indicated. .Said #9 shaft, 3, is j ournaled in a bearing, 4:, mount ed in a case,.5, in which the operating parts are inclosed. I v a "@is a field ring encompassing the magnet except as to'a short distance at which a gap, 6, is' made in the field ring for a purpose hereinafter explained This field ring is bi- Y inetallic, comprising an inner lamina, 6", of magnetic metal, as soft iron or steel, and an outer lamina, 6, of metal having a higher co-eflicient of expansion under change of temperature thanthe inner lamina, copper or brass being'suitable, for the purpose. The field-ring, 6, is fixedly secured in its'position about the ma et .by being fastened to adepend'ing arm, of a plate, 7, which ex This-invention relates primarily to in. strumentsin which a magnet and a non tends across the magnet in front of the same Specification of Letters Patent. P t t d 30, 19 3 i v Application filed January 18, 1913.;- Serial No. 742,781.

and is supported by posts, 9, 9, which ex tend from the bearing, 4. .The inner diameter of the field ring issuificicntly greater than the outer diameter of the magnet to allow space between the two for the depending flange, 10, of a cup disk whichconstitutes the drag element of electrically-conductive 'and non-magnetic. metal, as aluminum, said drag element being mounted upon a spindle,

11, which is stepped in the shaft, 3, axially chambered to. admit the spindle within the shaft. An upper bearing, 12, for the spindle isinounted upon the plate, 7, and above said hearing the spindle is connected to the inner endof the biasing spring, 1%, whose outer end is connected at 15, to the plate, 7.

The flange, 10, constituting the drag element is exteriorl'y graduated and marked to indicate miles travel of the vehicle to which the instrument is attached, andthis' graduation is- YlSlble through the gap, ti a-1 in the field ring andthrough an opening opposite said gap in the face plate. 1.6,

1 which closes the forward side of the case to 'complete the inclosure of the mechanism, a

reading point, 16, being projected from the margin'of the openingjinto the same and standing ad acent to the graduated scale on the drag element. Y

The mode of operation of this instrument,

for indication of speed is governed by well understood principles and similar to that of familiar instruments heretofore made. The specific feature which characterizesdt is the bi-metallic field ring, which-by its change of form consequent upon change of temperature, contracting or expanding it, according to familiar principles, moves it withrespect to the magnet -so as to change the Width of the annular gap between the. two in which the drag element is positioned, and thereby changing the form of the field and the influence of the field upon the drag element in a manner to compensate for errors inthe reading of the instrumentrwhich. would otherwise result from. temperature' changes. Upon rise of temperature, the conductivity of the drag element beingdiminished, the drag efiect is correspondingly diminished, and in the absence of compen sation the reading of the instrument will bev lowered and to that extent rende'red'inaccurate. The bi-metallic field ring described being contracted gadially by increase of temperature by reason of the outer lamina having the higher co-efiicientbf e p fi narrows-the annular net and the fieldr'ing,

satingly increases: the influence or effect of .tha t fiel l" upon -the drag element; and by.

; ment.

proper relation ofithe twolamina: of the ring, 3, this increasing .strength'of the field- -can he made to'accurately oifsetthe diminw v-ished susceptibility of the drag element-to the draggmg action, therby maintaining correctness 1n L'Incombination with a magnet, means fo'rLinfiuenc-ing the-form of the-magnetic ficl'd .comprising'a magnetic mass'proximate to said magnet, a-drag element positioned inthe magnetic field, and means for producing' relative movement of the magnet and drag. element,said-magnetic mass being comprised in a lei-metallic member mounted for movement toward and from the-magnet by a changeof its form under theinfluence of temperature change;

i 2. Inp'ombination witha -magnet, means for *llii'lum-igilig the formof the I magnetic" field comprising a magnetic mass proximate to saidmagnet, a drag element positioned in the magnetic field, and means for produc-' ing relative movementof thejmagnet and 'magnct-ic mass -being comprised in a laminated hi metallic member in the form of asplit ring encompassingthe. flange of the drag element, said men'lber being fixedly mounted atlone point n'ith't-he remainder fieldbetween' the magand thereby compenthe readings -of the instru;

element' about the axis. of the laden-said magnetic mass'bemg comprised n a lamifree for movement toward and the magnet by a change ofits form influence of temperature-change- 4. In combination with amagnet,- means for influencing the form of theg'rmr'gfietic field comprising amagnetic mass pro'ximate to "said magnet, a drag element in the-form of a flanged disk mounted with its flangem the magnetic field encompassing the path ofthe magnet poles, and means -for -fproduc--.

ing relative rotation of the magnet" and the drag element, one end of said memberbeing fixedly mounted and the remainder being free for movement toward and from the magnet by a change of its. form under;

the influence of temperature change .drag element about-the axis of the latter, said magnetic ,mass being comprised in a laminated bi-metallic member inthe form' of a: split ring encompassing thefliing'e 1 -5. In combination ,witha magnet, mea'nsi for influencing the form of the magnetic-t field comprising a magnetic mass proximate to said magnet, a drag element'in the ,form

of-a flanged disk mounted -with its flange in the magnetic field encompassing the path of the magnet-poles, and means 'for producs ing relative rotation of th magnet and draguated iii-metallic member in-the form of a.

split ring encompassing the flange of .the

ing fixedly mounted and the remainder,

drag element, one end of said mer'nber,be n

ing free for movementtowardand,' from the magnet by a change of its formimder.

- the influence of-temperature ;change,'. the;-

flange of the drag element being provided. with a scale, the opening between the ends" of the split ring member being suflicient to permit reading of the .scale, and an, ,index point fixedat said opening proximate. to these-id scale. w A

Intestimony whereof, I have hereunto; setmy hand. at Chicago, 111., this-2nd day. of'JarL, 1.912% 4 lVitns'se s:

C. B. Spurn, Smxnorn Hposoxr JOHN K. sT waRn: 

